1. Field of the Invention
The present invention relates to a display device that displays an image of plural colors. More particularly, the present invention relates to a display device capable of realizing a high-definition display panel while maintaining display quality.
2. Description of the Related Art
In a display device in which a plurality of display elements is arranged on a display panel in a matrix form, active-matrix driving is generally used in which, when switching elements arranged in the respective display elements are sequentially turned on by scanning lines connected to the switches of the switching elements, display control voltages corresponding to display data are supplied to the respective display elements through data signal lines connected to the input side of the switching elements.
These display elements are display elements that display images of any one of the three colors of red, green, and blue, and one pixel is constituted by adjacent display elements of the three colors which are sequentially arranged. The respective pixels are generally repeatedly arranged in the vertical and horizontal directions.
In this case, generally, one data signal line is connected to a plurality of pixels arranged in the vertical direction, and between the data signal line and each of the display elements of the three colors, an element-select switching element of the corresponding color is connected. Between the display element of each color and the element-select switching element of the corresponding color, a sub-data signal line is connected. A pixel data write period which is a period where display control voltages corresponding to display data are supplied to one pixel is divided into three sub-periods, the element-select switching elements of the corresponding colors are sequentially turned on during each of the three sub-periods When the element-select switching element is turned on during the corresponding sub-period, a display control voltage corresponding to the display data is supplied to the corresponding display element of the corresponding color of the pixel.
Display control voltages corresponding to display data which will be written to the corresponding display elements of the corresponding pixels are sequentially applied to the data signal lines by a data signal line driving circuit. The display data of the respective display elements of the respective pixels are input to the data line driving circuit as digital signals. The data line driving circuit includes a plurality of data line voltage generation circuits corresponding to the respective data signal lines. Each data line voltage generation circuit includes a DA converter that converts the display data (digital signal) of the corresponding display element to a display control voltage which will be applied to the corresponding data signal line. The DA converter is generally called a decoder.
The display data is described as a gradation value corresponding to display luminance. For example, in the case of 6-bit gradation, the gradation value is any value from 0 to 63. Generally, the higher the luminance, the larger the gradation value it expresses is. A gradation voltage, which is a display control voltage that should be applied to a data signal line so as to correspond to a certain gradation value, is different for each color. Therefore, a gradation voltage generation circuit unit that outputs gradation voltages for all gradations for each of the three colors is provided in the display device.
FIG. 14A is a schematic circuit diagram showing pixels which are arranged in a general pixel arrangement and a data line driving circuit 11 which supplies display control voltages to these pixels, both of which are provided in a display device according to the related art. FIG. 14B is a diagram showing changes over time in the driving of element-select switching elements and the data line driving circuit 11 shown in FIG. 14A.
As described above, element-select switching elements of the colors of red, green, and blue are sequentially turned on during a data write period for these pixels, and data line voltage generation circuits 20 sequentially supply display control voltages to the display elements of the colors of red, green, and blue of the corresponding pixels through corresponding data signal lines 100 and corresponding sub-data signal lines 101. That is, a plurality of the data line voltage generation circuits 20, which is provided in the data line driving circuit 11, simultaneously applies display control voltages corresponding to the display elements of the same color of the three colors to each of the corresponding data signal lines 100. Moreover, each DA converter, which is provided in each of the data line voltage generation circuits 20, simultaneously selects and outputs a gradation voltage out a gradation number of graduation voltages output by the gradation voltage generation circuit unit of the same color.